Device for cooling at least one piston of an internal combustion engine

ABSTRACT

A device for cooling the pistons of an internal combustion engine by a lubricating oil pump which supplies oil from the lubricating oil circuit to at least on the base side of each piston through at least one supply line having an outlet opening and at least one valve. The at least one valve is a check valve which does not permit oil to be supplied until after a defined pressure is achieved in the lubricating oil circuits and a control unit regulates the lubricating oil pump so as to provide variable pressure in the lubricating oil circuit as a function of engine load.

This application is a continuation of International Patent Application PCT/EP2005/003783, filed Apr. 11, 2005, and claims the priority of German Patent Application DE 10 2004 017 909.3, filed Apr. 13, 2004, the disclosures of which are expressly incorporated by reference herein.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a device for cooling at least one piston of an internal combustion engine.

Such a device and method are known from German patent publication DE 199 33 363 A1. According to the disclosure, the supply of lubricating oil for cooling the pistons of the internal combustion engine is controlled by a solenoid valve which is actuated as a function of the engine parameters of oil temperature, water temperature, or oil pressure. In this manner the pistons are cooled, for example only after a cold-start phase has elapsed, thereby ensuring rapid heating of the combustion chamber.

Furthermore, a method is known from German patent publication DE 102 06 769 A1 for operating an internal combustion engine with engine braking and controllable piston cooling, the piston cooling being reduced in engine braking mode. As a result, the piston is not excessively cooled in engine braking mode. The development of increased play between the piston and the cylinder wall and an associated increased flow of air from the combustion chamber into the crankcase chamber (blow-by) is thus avoided.

The object of the invention is to provide a method which ensures optimized piston cooling in such a way that the overall efficiency of the internal combustion engine is improved.

According to the invention, a check valve is used in a known manner in the main supply line, or one check valve is used for each supply line, and according to the invention the lubricating oil pump regulates the pressure in the lubricating oil circuit to adapt to different operating conditions for the internal combustion engine as a function of load. As the result of the load-dependent regulation of the lubricating oil pump, a check valve may be used which operates with an increased opening pressure compared to a check valve in a system without a lubricating oil pump that is regulated as a function of load. In this manner unnecessary piston cooling is avoided in many operating conditions.

In one refinement of the invention, the lubricating oil pump is regulated as a function of additional operating parameters, in particular as a function of the rotational speed of the internal combustion engine and/or the temperature of the internal combustion engine and/or the coolant temperature of the internal combustion engine and/or the lubricating oil temperature.

Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first device according to the embodiments of the invention.

DETAILED DESCRIPTION

FIG. 1 shows a schematic illustration of a device for cooling the pistons 2 (or the at least one piston) of an internal combustion engine. In the embodiment illustrated, the device comprises a lubricating oil pump 10 which via a supply line 12 supplies the piston 2 with lubricating oil for cooling. A check valve 14 is provided in the supply line 12, between the lubricating oil pump 10 and the outlet opening 12 a of the supply line 12. According to the invention, the lubricating oil pump 10 is controlled by a control unit 20 which ensures that the lubricating oil pump 10 is regulated as a function of the determined load on the internal combustion engine. The lubricating oil pump 10 preferably is controlled via the control unit 20 (a motor control unit, for example) by means of a characteristic field regulation as a function of a plurality of operating parameters. In addition to the regulation or control of the lubricating oil pump 10 as a function of the load, the control is performed as a function of the engine temperature, the engine rotational speed, and/or the lubricating oil temperature. As a result of the load-dependent regulation of the lubricating oil pump 10, the check valve 14 may be designed for an increased opening pressure. Whereas a check valve 14 for conventional, non-load-dependent regulation of the lubricating oil pump of an internal combustion engine in a motor vehicle is designed for an opening pressure of approximately 2 bar (in order to ensure sufficient piston cooling in all critical circumstances), for the load-dependent regulation of the lubricating oil pump 10 according to the invention a check valve 14 is used having an opening pressure that is higher by comparison, for example, an opening pressure of 3 bar.

Of course, the plurality of valves (one valve per supply line) may be replaced by the use of a single valve in a main supply line which is connected to the supply lines (not illustrated).

The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof. 

1. A device for cooling at least one piston of an internal combustion engine, comprising: a lubricating oil pump which supplies oil from a lubricating oil circuit to the at least a base side of at least one piston through a supply line having at least one outlet opening; at least one valve in the supply line, wherein the at least one valve is a check valve which does not permit oil to be supplied to the at least one piston until after a predefined pressure is achieved in the lubricating oil circuit; and a control unit which controls the lubricating oil pump to provide a variable pressure in the lubricating oil circuit as a function of load on the internal combustion engine.
 2. The device according to claim 1, wherein the check valve operates at a higher opening pressure than a check valve in a system in which lubricating oil pump operation is not regulated as a function of load.
 3. The device according to claim 1, wherein the control unit controls the lubricating oil pump to regulate pressure in the lubricating oil circuit as a function of additional operating parameters, including at least one of engine rotational speed, engine temperature, coolant temperature, and lubricating oil temperature.
 4. A method for cooling at least one piston of an internal combustion engine, comprising the acts of: creating a variable pressure in a lubricating oil circuit with a lubricating oil pump controlled by a controller; and supplying lubricating oil through a supply line having at least one outlet opening and at least one valve in the supply line and to at least a base side of at least one piston; wherein the at least one valve is a check valve which does not permit oil to be supplied to the at least one piston until after a predefined pressure is achieved in the lubricating oil circuit; and the control unit controls the lubricating oil pump to provide the variable pressure in the lubricating oil circuit as a function of load on the internal combustion engine.
 5. The device according to claim 4, wherein the check valve operates at a higher opening pressure than a check valve in a system in which lubricating oil pump operation is not regulated as a function of load.
 6. The device according to claim 4, wherein the control unit controls the lubricating oil pump to regulate pressure in the lubricating oil circuit as a function of additional operating parameters, including at least one of engine rotational speed, engine temperature, coolant temperature, and lubricating oil temperature. 